Effect of niobium on ductility drop cracking susceptibility of nickel-base alloys

The strain-to-fracture was used to determine the strain threshold and temperature which cause cracking and quantify the DDC(ductility dip cracking)susceptibility of HS690 filler metals which have different content of Nb.The morphology and distribution of precipitation was analyzed by trasmission electron microscope.The results show that adding Nb to HS690 filler metal will improve the quantity and morphology of the second phase(Nb, Ti)C in grain boundaries, the condition of grain boundaries and DDC susceptibility of HS690 filler metal.